Does System Restore undo software (non-bios) overclocking? Also, if the clock speed is too high, will it let you boot into the F8 System Restore menu?
Depends. if you used some kind of "make overcloking persistent" option in overclocking software, then it may permanently set the hardware at overclocked rate. If this is not the case then the changes made by the software are temporary and valid till next reboot only.
Advanced Boot Menu (F8) has nothing to do with overclocking. Ofcourse it will boot. :)